makes some good points. agree from screening prospective (not on treatment->screen->find disease->treat->improve outcomes), there is no RCT-> show "screening" helps. I may even go further & said in 2015 (apply more in 2018) do we need screening (even with CAC?) 
#1 so basically statin are great, we decide candidates based on PCE in asymptomatic, but what are the tradeoffs (too many eligible, PCE overestimates, patient uncertain & reluctant). 
#2 so many people argue about this thing, "Power of Zero"...what exactly is the evidence? does it really portends to a low risk, even those "traditionally" at high risk? 
#3, so lets assume, pt PCE risk is 12%, uncertain, whats is the likelihood if use this option (via SDM) that the consumer (pt) will have a CAC=0? 
#4, ok there is a nearly 4 out of 10 chance, wud it reduce my ascvd risk (including strokes) below a threshold (average <5% 10 yr risk) where per ACC/AHA guidelines I may not be recommended statin? 
#5 good so far, but truly where would i get a real value in reclassifying risk to maximize yield and help with a group to move above a risk level where our society suggests statin and many below where not beneficial? Will experts agree on this? 
# 6 moving as physicians, I am sure you are wondering why I can't use other much easier test to get the same power of down risking that may inform individual decisions? unfortunately none provides that power! 
# 7 ok helps at individual level, but CAC costs (upstreams), statins work, wouldn't treating all be more cost effective? there are genuine societal concerns! well good news both are equally effective, allowing us to use either approach based on pt preferences. 
#8, good arguments, but what does other real experts think about CAC role (if any)? 
#9 so humbly, I think the question is clearly shifting from "why" CAC almost decade ago to "why not" in 2018. Also this is in whom u should consider and potential management options (all with spirit of shared decision making) 
# 10, closing statement..think hard, CAC not a screening test, but a decision test..if the goal is to have SDM, I feel challenging from ethical stand point not to disclose this information. Lets embrace uncertainty and allow pt to be in the driver seat for decision making. 
